At present, liquids or fluids stored in tanks, e.g. hydrocarbon liquids, are under constant surveillance, particularly in installations such as oil refineries, for purposes of reliable economic management and to achieve a high degree of safety with such large volumes of fuel.
In order to measure the level of the liquids, proposals have already been made for systems in which a substantially vertical electrical transmission line is partially immersed in the fluid and is connected to a source of electrical measuring pulses which are applied to the line. The measuring pulses are partially reflected by the plane of dielectrical discontinuity constituted by the free surface of the liquid in the tank (e.g. a hydrocarbon) where it meets the atmosphere occupying the empty portion of the tank.
Reference may be made to French patent application number 73 39188 filed Nov. 5, 1973 or Great Britain No. 1,448,282 published Sept. 2, 1976 by the present Applicant for a description of this type of apparatus.
The apparatus described provides a good measurement of the level of the separation between the liquid constituted by a hydrocarbon and the upper empty portion of the tank. However, in most cases, the fluid constituted by the hydrocarbon is floating on bottom water, and measuring the liquid level corresponding to the first transition between the atmosphere and the hydrocarbon does not give the real depth or the real volume of the hydrocarbon contained in the tank. It is therefore not possible to measure the real depth of one of the fluids on a permanent basis given the presence of one or more other fluids.
In addition, in order to provide complete surveillance of such tanks, it is advantageous to be able to measure both the temperature of the atmosphere occupying the empty portion of the tank and of the fluid, e.g. the hydrocarbon, constituting the first transition with the atmosphere in the tank, with such measurements being performed independently of the real level of the transition.
Present temperature measuring devices must therefore either include measuring probes mounted on floats, or else they must provide a plurality of probes distributed over the inside surface of the tank, for example.
The object of the present invention is to remedy the above-mentioned drawbacks by implementing a single apparatus for measuring storage parameters such as level and temperature of liquids or fluids of different densities in a tank.
Another object of the present invention is to implement apparatus for measuring the storage parameters of liquids or fluids in a tank making it possible to obtain the effective depth of each of the fluids or liquids of different density in the presence of other fluids or liquids.
Another object of the present invention is also to provide apparatus for measuring the average temperature of a given fluid or liquid contained in a tank, taking account of the temperature value of the vapor phase of said liquid or fluid constituting the top atmosphere or void in the tank.